Code No. P1272: Pressure Limiter Malfunction

OPERATION

Refer to Code No. P0191: Rail Pressure Sensor Range/Performance Problem .
Refer to Code No. P0192: Rail Pressure Sensor Circuit Low Input .
Refer to Code No. P0193: Rail Pressure Sensor Circuit High Input .
Refer to Code No. P0628: Suction Control Valve Open .
Refer to Code No. P0629: Suction Control Valve Battery Short .

FUNCTION

The engine-ECU controls the fuel discharge rate using the suction control valve.
The engine-ECU monitors the signals input from the rail pressure sensor.
The engine-ECU checks whether the pressure limiter valve is open, based on changes in the signals input from the rail pressure sensor (rapid drop of pressure after it goes extremely high).

TROUBLE JUDGMENT

Check Conditions

Battery positive voltage is 8 - 16V
Engine speed is 600 r/min or more
2 seconds later after the ignition switch has been in "ON" position or the engine has started up
Rail pressure sensor is normal

Judgment Criterion

After a pressure higher than the pressure of the pressure limiter opening valve is detected, fuel leakage diagnosis (supply pump discharge rate excessive) is detected within the predetermined time.

FAIL-SAFE AND BACKUP FUNCTION

None

PROBABLE CAUSES

Failed suction control valve
Failed fuel system
Failed common rail assembly
Open/short circuit or harness damage in suction control valve circuit or loose connector contact
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code

Q. Is any other diagnosis code than P1272 set?

	Inspection chart for diagnosis codes (Refer to ).

	Go to Step 2 .

STEP 2. Check the fuel filter contamination.

Q. Is the check result normal?

	Go to Step 3 .

	Replace the fuel filter then replace the common rail assembly and fuel injection tubes.

STEP 3. Release the air from the fuel line.

After releasing the air from the fuel line, continue idle operation for about five minutes and recheck for abnormal symptoms.

Q. Does trouble symptom persist?

	Replace the common rail assembly and common tubes.

	Go to Step 4 .

STEP 4. Check suction control valve itself.

Check suction control valve itself (Refer to ).

Q. Is the check result normal?

	Go to Step 5 .

	Replace the suction control valve. After replacing the suction control valve, learn the supply pump. (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).

STEP 5. Connector check: C-116 engine-ECU connector and A-29 suction control valve connector

Q. Are the check results normal?

	Go to Step 6 .

	Repair or replace the connector.

STEP 6. Check harness between C-116 (terminal No. 17) engine-ECU connector and A-29 (terminal No. 1) suction control valve connector.

Check power supply line for open/short circuit and damage.

Q. Is the check result normal?

	Go to Step 7 .

	Repair the damaged harness wire.

STEP 7. Check harness between C-116 (terminal No. 37) engine-ECU connector and A-29 (terminal No. 2) suction control valve connector.

Check earthing line for open/short circuit and damage.

Q. Is the check result normal?

	Go to Step 8 .

	Repair the damaged harness wire.

STEP 8. Perform output wave pattern measurement at A-29 suction control valve (Using an oscilloscope).

Engine: Idling
Connect the oscilloscope special patterns pickup to engine-ECU terminal No. 17 and earth.

OK: The waveform should show a pattern similar to the illustration of inspection procedure using an oscilloscope (Refer to ).

Q. Is the check result normal?

	Go to Step 9 .

	Replace the engine-ECU then replace the common rail assembly and fuel injection tubes. After replacing the engine-ECU, register the injector identification code and learn fuel injection. (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).

STEP 9. Replace the common rail assembly and fuel injection tubes.

After replacing the common rail assembly and common tubes, re-check the trouble symptoms.

Q. Does trouble symptom persist?

	Replace the suction control valve. After replacing the suction control valve, learn the supply pump. (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).

	The check is end.